C30 Transmission Warning Light

Hello. I have a C30 as well and a very similar thing happened to me. Warning lights, rough shifting... Everything points to this gearbox sensor issue. In my case, it was eventually linked to the gearbox oil level. When the oil level is low, the sensor doesn't read properly, which then triggers all of these symptoms. Have you checked the gearbox oil level?

Thanks for the quick reply! I haven't checked the gearbox oil level yet, to be honest. I was planning on doing that this weekend. But how did you finally resolve it? Did you just top up the oil, or was there more to it?

Well, in my case, just topping it up didn't completely solve it. The damage was already done. The shifting remained problematic. Ultimately, I had to take it to a workshop. They replaced the sensor and topped off the oil. I would strongly suggest you have a shop take a look at it to be safe.

Thanks a lot for your help! I took your advice and brought it to a workshop. Turns out, it was indeed the gearbox oil temperature sensor and the oil level was low. They replaced the sensor, topped up the oil, and did a full diagnostic. Cost me about 365€, but now it's shifting smoothly again. Really appreciate the insight!